Axillary Artery

The major variations of the axillary artery are discussed here; there are many!

Occasionally, it gives rise to the radial artery or, more rarely, to the ulnar
artery. Still more rarely, it gives rise to the interosseous artery or a vas
aberrans.

It may give rise to a common trunk from which may arise the subscapular, anterior
and posterior circumflex humeral, profunda brachii, and ulnar collateral arteries.
The branches of the brachial plexus may surround this common trunk, but not
the main brachial artery.

In some cases, the brachial artery appears to be an enlarged "vas aberrans,"
and the common trunk to the brachial artery, the lower portion of which has
been obliterated. A vas aberrans, according to Quain, is a long, unusually slender
vessel that originates either from the axillary or the brachial and unites with
forearm arteries or their branches. The vas aberrans may extend into the hand
to join the superficial palmar arch. In eight of nine cases, the aberrant vessel
joined the radial artery; hence it rarely joins the ulnar.

The axillary artery may be represented by two parallel vessels that arise
from the first part of the subclavian and continue distally as the ulnar and
radial
arteries.(Calori)

The first part of the axillary may also provide an accessory thoracoacromial
artery. The third part of the axillary artery is occasionally covered by a muscular
slip (an axillary arch muscle) derived from the upper part of the tendon of
latissimus dorsi; this muscular slip is "always" present in early fetal life,
but it usually atrophies later. Axillary arch muscles may persist and may be
clinically important. In an article by Alexander Ramsay, Account of unusual
conformations of some muscles and vessels, 1813 (see reference list for full
citation) the author remarks, " that in 1795, he discovered a transverse muscle
of the axilla, which may account for the liability of some subjects to swelling
of the axillary glands (nodes) on occasions of violent exertion. This body is
composed of an oblong muscle, stretched from the pectoral muscle to the latissimus
dorsi and teres major, which in its violent contractions, must prove inconvenient
to the axillary arteries, veins, and nerves, which lie beneath this muscle.
It was not known in Edinburgh or London, when I demonstrated it, and it is now
detected in one of thirty subjects, when dissectors are attentive." The muscle
is now known as an axillary arch muscle. It has been well studied by Langer
(and others) whose name is often given with it, e.g. Langer's muscle. A more
suitable name would be, perhaps, Ramsay's muscle. The Langer citation can be
found in Part 1, Muscular System of the present series under Axillary Arch Muscle.

Any of the following branches that normally arise from the subclavian artery
may also arise instead, from the axillary artery, either from a common trunk
or in groups: the inferior thyroid, ascending cervical, superficial cervical,
deep cervical, internal thoracic, transverse cervical, suprascapular or the
anterior and posterior circumflex humerale arteries from a common trunk. A trunk
from the axillary has been reported giving rise to the anterior and posterior
circumflex humeral, the subscapular, the superior profunda, and the inferior
profunda arteries (Walsham).

Unusual branches of the axillary include a glandular artery to lymph nodes
and skin of the axilla (so called alar thoracic artery) and an accessory lateral
thoracic artery.

Heuston reported on three interesting axillary arteries as follows. An aberrant
artery, which arose from the axillary, above the origin of the subscapular branch,
passed in the arm to the inner (medial) side of the brachial artery, to unite
with the radial about two inches below its commencement. In this case the brachial
artery bifurcated about one inch (2.54 cm) above its normal position. In a second
case, the unusual artery also arose from the axillary, opposite the upper border
of teres major muscle, and passing between the heads of the median nerve, proceeded
down the outer (lateral) side of the brachial artery, to unite with the radial
recurrent, which was large in size in the antecubital fossa. In the third case,
the suprascapular artery, arising from the axillary opposite the second rib,
passed upwards beneath the clavicle through the cords of the brachial plexus,
and having given a branch to the subscapularis muscle, passed beneath the transverse
ligament (of the scapula) with the suprascapular nerve, to be distributed as
usual.

Konarik, Katchlik, and Baca reported a case with "a coincidental variation of the axillary artery: with a brachioradial artery (radial with a high origin at the end of the axillary artery) and an aberrant posterior humeral circumflex artery passing under the tendon of the latissimus dorsi muscle.

Walsham, W.J. (1880) Anatomical variations: An account of a few of the more
interesting abnormalities that have occurred in the dissecting-rooms during
the past seven years; with remarks on their morphological significance, and
their bearing on the practice of surgery. St. Bartholomews Hospital Reports
16:91.

Winslow, R. (1883) A study of the malformations, variations, and anomalies
of the circulatory apparatus in man. Annals of Anatomy and Surgery 7:18-19.

Variations in Branches of Axillary ArteryThe following variations have been recorded in the branches of the axillary
artery.

The first part may give rise to the dorsal (posterior) scapular artery (0.5%
of individuals, Poynter). Pellegrini found the first branch to be one to serratus
anterior (20% of individuals) and Poynter found this same vessel in 42% of 200
cases.

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